experimental: portfolio features (justified layout, unlisted pages, captions, per-album grid, focal point, nav links, cover hero) (#431)

## Was ist das?

Sieben neue Portfolio-Features, alle als **experimental** gekennzeichnet
— in YAML-Kommentaren, Admin-Panel-Labels und Commit-Scopes, damit sie
einzeln nachvollziehbar und revertierbar bleiben.

## Features (je ein Commit)

| Commit | Feature |
| --- | --- |
| `justified rows gallery layout` | Neues Grid-Layout `justified`:
zeilenbasiert, gleiche Höhen, volle Breite — Flexbox ohne JS-Messung,
letzte Zeile bleibt natürlich klein |
| `hide subpages from navigation` | `hidden: true`: Seite aus
Nav/Homepage raus, per Direktlink erreichbar — im Gegensatz zu `enabled:
false` (404) |
| `lightbox captions` | Immich-Asset-Description als Bildunterschrift im
Info-Panel; EXIF-Route liefert bei `exifOnHover: false` jetzt nur noch
die Caption statt 403 |
| `per-album grid overrides` | `grid:` pro Album-Eintrag, Präzedenz
global < Subpage < Album |
| `per-album cover focal point` | `coverPosition:` → `object-position`
auf Cover-Karten, strikt validiert |
| `external links in header navigation` | `navLinks:` in settings.yaml,
nur http(s), sanitisiert |
| `cover splash hero style` | `heroStyle: cover`: Fullscreen-Splash mit
Enter-Link ins Portfolio |

Alle Optionen sind im Admin-Panel editierbar (PageBuilder /
SettingsEditor).

## Tests

- 356 Unit-Tests grün (13 neue: deriveGallery hidden/grid/coverPosition,
sanitizeNavLinks, EXIF-Route-Captions, justified-Layout-Validierung)
- `npx tsc --noEmit`: 0 Fehler
- `npm run build`: sauber
- Justified-Zeilenmathematik und Cover-Splash per Browser-Harness
visuell/numerisch verifiziert (volle Zeilen enden exakt an der
Containerkante, letzte Zeile bleibt natürlich)

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: ralksta <ralksta@users.noreply.github.com>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: lancetm714 <108419425+lancetm714@users.noreply.github.com>

content/gallery.yaml.example

@@ -51,12 +51,17 @@ subpages:
     title: "My Creative Projects" # Optional: Header title, defaults to Navigation key ("Projects")
     subtitle: "A collection of 2026 highlights in 35mm film." # Optional: Sub-text for headers
     password: "your-password" # Optional protection
+    # hidden: true # EXPERIMENTAL: reachable by direct link, but not shown in navigation
     albums:
       - "album-uuid-5"
       - "album-uuid-6":
           title: "Private Project #7"
           description: "Shot on 35mm film in Vienna, spring 2025." # Optional: shown below album title
           password: "scrypt:..." # Recommended: secure hash (generated via logs)
+          # grid: # EXPERIMENTAL: per-album grid override (wins over page/global grid)
+          #   layout: "justified"
+          #   columns: 2
+          # coverPosition: "50% 25%" # EXPERIMENTAL: focal point for the cover crop ("top", "center bottom", "50% 25%")
 
 # ── Subpage with Sections ──────────────────────────────────────────
 # Use sections to group albums by location, theme, or any other logic.

content/settings.yaml.example

@@ -39,7 +39,7 @@ theme:
   # accent: "#e60012"
   # photoFrame: "passepartout" # none, passepartout, shadow
   # grain: true
-  # heroStyle: "split" # split, fullbleed, minimal, stacked, typographic, mosaic
+  # heroStyle: "split" # split, fullbleed, minimal, stacked, typographic, mosaic, cover (EXPERIMENTAL)
   #   Note: "mosaic" needs at least 3 hero images in gallery.yaml (optimal: 6)
 
 # ── Grid configuration ───────────────────────────────────────────
@@ -47,7 +47,16 @@ grid:
   columns: 3
   gap: 12
   aspectRatio: "1" # "1" (square), "3/2", "2/3", "16/9", "auto"
-  layout: "masonry" # masonry, uniform, showcase, filmstrip, editorial-flow
+  layout: "masonry" # masonry, uniform, showcase, filmstrip, editorial-flow, justified (EXPERIMENTAL)
+
+# ── Navigation ────────────────────────────────────────────────────
+# EXPERIMENTAL: external links appended to the header navigation.
+# Only http(s) URLs are allowed; they open in a new tab.
+# navLinks:
+#   - label: "Shop"
+#     url: "https://shop.example.com"
+#   - label: "Instagram"
+#     url: "https://instagram.com/your-handle"
 
 # ── Footer & Social ──────────────────────────────────────────────
 footer: